When Londoner Jamie Liang reached the Eurostar security checkpoint at London St Pancras International he put his possessions on the conveyor belt and entered the body scanner. It beeped. Instead of searching him, he said officials summoned him to one side, demanded to see his passport and, when he repeatedly asked why, threatened to call the police. The reason was eventually explained loudly, he says, in front of other passengers: security staff were unclear whether he was male or female and wanted proof of his sex before deciding which official should search him.